Improve semaphore documentation

Move documentation from semaphore.h to semaphore.c as requested by
Andrew Morton.  Also reformat to kernel-doc style and add some more
notes about the implementation.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

1 files changed, 2 insertions, 37 deletions

diff --git a/include/linux/semaphore.h b/include/linux/semaphore.h
index a7125daaff9..9cae64b00d6 100644
--- a/include/linux/semaphore.h
+++ b/include/linux/semaphore.h
@@ -4,8 +4,7 @@
  *
  * Distributed under the terms of the GNU GPL, version 2
  *
- * Counting semaphores allow up to <n> tasks to acquire the semaphore
- * simultaneously.
+ * Please see kernel/semaphore.c for documentation of these functions
  */
 #ifndef __LINUX_SEMAPHORE_H
 #define __LINUX_SEMAPHORE_H
@@ -13,11 +12,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 
-/*
- * The spinlock controls access to the other members of the semaphore.
- * 'count' represents how many more tasks can acquire this semaphore.
- * Tasks waiting for the lock are kept on the wait_list.
- */
+/* Please don't access any members of this structure directly */
 struct semaphore {
         spinlock_t              lock;
         unsigned int            count;
@@ -46,41 +41,11 @@ static inline void sema_init(struct semaphore *sem, int val)
 #define init_MUTEX(sem)         sema_init(sem, 1)
 #define init_MUTEX_LOCKED(sem)  sema_init(sem, 0)
 
-/*
- * Attempt to acquire the semaphore.  If another task is already holding the
- * semaphore, sleep until the semaphore is released.
- */
 extern void down(struct semaphore *sem);
-
-/*
- * As down(), except the sleep may be interrupted by a signal.  If it is,
- * this function will return -EINTR.
- */
 extern int __must_check down_interruptible(struct semaphore *sem);
-
-/*
- * As down_interruptible(), except the sleep may only be interrupted by
- * signals which are fatal to this process.
- */
 extern int __must_check down_killable(struct semaphore *sem);
-
-/*
- * As down(), except this function will not sleep.  It will return 0 if it
- * acquired the semaphore and 1 if the semaphore was contended.  This
- * function may be called from any context, including interrupt and softirq.
- */
 extern int __must_check down_trylock(struct semaphore *sem);
-
-/*
- * As down(), except this function will return -ETIME if it fails to
- * acquire the semaphore within the specified number of jiffies.
- */
 extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
-
-/*
- * Release the semaphore.  Unlike mutexes, up() may be called from any
- * context and even by tasks which have never called down().
- */
 extern void up(struct semaphore *sem);
 
 #endif /* __LINUX_SEMAPHORE_H */